General Model Output Discussion Thursday December 24Th:

[Geordiesnow]

At least the GFS continues it's current trend of having the low quite far South for the cold air and ne'lies to dig in and milder air stays to the extreme South and the continent but even the former gets into the colder air quickly enough.

Whilst on paper the ECM looks great in it's earlier part of the run, the uppers are not that cold, this is due to the angle of the low and the fact that the low is not South enough on the first part of the run. However it would not take much adjustment for the colder air to dig in like the GFS.

The UKMO has the low too far North hence why some of you are wondering why you got such mild temps on the 5 day forecasts, these can change very quickly however if the low alters it's position South as the cold air from the North would dig in.

All in all though, fantastic output but it has to be taken in stages and stage 1 is to get that low the correct angle and position. Until we know about that, then we can concentrate on about strength of any flow and perhaps how long it might last for.

[TEITS]

I bet that does not stop you looking at the models though (and using it as an a reason when we don't get what we want)!

Always handy to have an excuse mate.

On a serious note and to be honest its asking a bit much to expect superb F.I runs every time. Even prior to our recent cold spell I remember a shocking 12Z ECM run.

Anyway im going to stick around for a bit longer because according to the radar something is developing just to my W and due to favourable dewpoints/temps I may even see a technical white xmas!!

[Weather-history]

Far too much fussing over 240hr+ charts, IMO, when as we have seen in recent days of the uncertainties in the foreground, thats where we should really be looking at. There may or may not be a major snow event.

I mean this was the 18z op run of 3 days ago for New Year's Day, no cold weather there

http://91.121.94.83/modeles/gfs/archives/gfs-2009122018-0-276.png?18

A thing that I have heard around this time of the year, is that less data is collected and processed into the computers because its Christmas. Less readings are made.

How true is that or is it a myth?

Edited December 24, 2009 by Mr_Data

[03jtrickey]

Wow, just seen the ensembles. Remarkable consistency all through, at least in terms of 850 temperature! It's going to be cold...

Whatever happened to the mild blip? It's gone!

http://charts.netweather.tv/ensimages/ens.20091224/18/t850Gloucestershire.png

http://charts.netweather.tv/ensimages/ens.20091224/18/t850Aberdeenshire.png

Really really exciting model viewing now.

Merry Christmas All :lol:

[kold weather]

I'm not sure I buy that idea for Xmas Eve but it wouldn't surprise me if there is a slight reduction in the global data, though clearly automated data will still be a big part of the data going into the models, upper features may not be modelled as well I'd have thought.

Ensembles look pretty decent for the most part, a big majority are cold throughout.

[snowlover2009]

another excellent gfs run. I have been thinking if that low was in the correct position that is being sown on gfs by next week, then i reckon i may be looky enough to get the snow, i mean i am not too far north when you think about it.

Edited December 24, 2009 by snowlover2009

[Cloud 10]

Gfs 18z great in the short term,not as good in the later part of the run,however it was an outlier for temps on the aberdeen ensembles....

....and also has little support for lower pressure over iceland at about the same timeframe.

[TEITS]

Remember I said earlier that the GEFS ensembles will begin to move the LP further S?

Well this is happening as the mean in Cambs is dropping.

http://charts.netweather.tv/ensimages/ens.20091224/18/t850Cambridgeshire.png

Look at the ensembles for Aberdeen.

http://charts.netweather.tv/ensimages/ens.20091224/18/t850Aberdeenshire.png

I have never seen ensembles like this before especially with regards to how prolonged the mean remains below -5C.

I will add that just to make my evening complete the Met O have released a warning for snow in Cambs tonight. Can it get any better!

Edited December 24, 2009 by THE EYE IN THE SKY

[swilliam]

Gfs 18z great in the short term,not as good in the later part of the run,however it was an outlier for temps on the aberdeen ensembles....

....and also has little support for lower pressure over iceland at about the same timeframe.

there is something wrong with the Netweather ensembles - this happened earlier. Here is the ensemble for London - no outlier

but still the mild blip un til this resolved - fantastic control run again

Edited December 24, 2009 by swilliam

[butler_son]

Wow, just seen the ensembles. Remarkable consistency all through, at least in terms of 850 temperature! It's going to be cold...

Whatever happened to the mild blip? It's gone!

http://charts.netwea...cestershire.png

http://charts.netwea...erdeenshire.png

Really really exciting model viewing now.

Merry Christmas All

I've found your mild blip James! On the ensembles, anyway...

[TEITS]

Synoptically the 18Z has much lower pressure around Iceland at +348 with a LP system measuring 980mb. The ensemble mean for this period is 1015mb.

So although it isn't strictly an outlier, it doesn't have much support from the other members.

http://91.121.94.83/modeles/gens/run/gens-21-1-348.png?18

[BLAST FROM THE PAST]

Merry Christmas all...weather warning...January will be bitterly cold with at least 2 weeks of lying lowland snow and sub zero temps....get used to it. I have to say this New year scenario is very very exciting. The 12 ECM shows the longevity likeliness of the next cold spell.....a Blast From The Past for sure.

regards

BFTP

PS some excellent analysis from some posters.

[swilliam]

Far too much fussing over 240hr+ charts, IMO, when as we have seen in recent days of the uncertainties in the foreground, thats where we should really be looking at. There may or may not be a major snow event.

I mean this was the 18z op run of 3 days ago for New Year's Day, no cold weather there

http://91.121.94.83/...18-0-276.png?18

A thing that I have heard around this time of the year, is that less data is collected and processed into the computers because its Christmas. Less readings are made.

How true is that or is it a myth?

Yes you are probably right about the too much fussing out at that timescale but the model output is so interesting it is fascinating to ponder over how it will evolve.

[Richard Lake]

Let me be the first to say, merry xmas all! Long may the models show good fortune. :lol: :lol:

[kold weather]

Synoptically the 18Z has much lower pressure around Iceland at +348 with a LP system measuring 980mb. The ensemble mean for this period is 1015mb.

So although it isn't strictly an outlier, it doesn't have much support from the other members.

http://91.121.94.83/...21-1-348.png?18

Yep, whilst the 18z is a cold run throughout the fact that it has little support for toppling the high so very quickly is good to see....most runs still keep some form of -ve NAO well into Jan...

Also worth nothing the 18z GFS was one of the further south runs on the ensembles, quite a few are still further north...however the op run is something that could happen...for my area if it doesn't get adjusted southwards I'm going to be getting a huge amount of rain and very very little snow...

[shuggee]

there is something wrong with the Netweather ensembles - this happened earlier. Here is the ensemble for London - no outlier

but still the mild blip un til this resolved - fantastic control run again

Nope - they are the same. You sure you are comparing like with like?

[snowlover2009]

I just cannot get excited, more really for the early part of next week. i fear i am going to be a bit too north for this low, yes i know it will chop and change, but i just cannot be certain that it wil work in our favour for us up north. i am not too far up north and this is the problem because i could just miss out by a few miles off this event. i am in the north of england but i am not exactly that far up to where newcastle and cumbria is.

However the output for midweek onwards suggests N-easterly flow which delivers here and will bring us snow. A good agreement for very cold air to come in, but its not a proper cold spell for me without a major snow event. feb was good, but it still isnt anything like the 70s or 80s with drifts up to second floor windows.

[TEITS]

I hope the mods forgive me for being off topic but I wanted to put this post on this thread due to its popularity.

I want to wish you all a Merry Christmas. Its been a wonderful experience these past few weeks on this forum and long may it continue.

[swilliam]

Great post Stewart! Deserves to be archived and put into one of the NetWeather guides :lol:

Thanks - I hope some people read it (including snowlover2009) - not a good time to be posting.

Edited December 25, 2009 by swilliam

[shuggee]

^^^ What Dave said. Happy Xmas from me too.

As I look out over 6" of snow :lol:

I'm starting to like the term 'positive feedback' - and we'll start a fresh thread in the morning :lol:

[swilliam]

I hope the mods forgive me for being off topic but I wanted to put this post on this thread due to its popularity.

I want to wish you all a Merry Christmas. Its been a wonderful experience these past few weeks on this forum and long may it continue.

And a Merry Christmas to you as well - we have all enjoyed your posts - there is nothing like a good ramp even though we always get told off for it.

[Richard Lake]

Yeah I wanted to wish everyone a merry christmas at the stroke of midnight, but some scrooge removed my post TEITS!! :lol: :lol:

Keep up the good work folks, I don't know very much about forecasting, but reading the posters here is always such a delight.

[grab my graupel]

Merry Christmas Everyone

Brian :lol: :lol:

[Guest]

^^^ What Dave said. Happy Xmas from me too.

As I look out over 6" of snow :lol:

I'm starting to like the term 'positive feedback' - and we'll start a fresh thread in the morning

Is that some fresh thread for a new pair of shorts Shuggs?? And who on earth gave you positive feedback about them??

Merry Xmas one and all :lol:

[Tom Montalbano]

Wrong thread I know but probably the most popular at the moment, so here goes.

Merry Xmas everybody.

:lol:

Regards,

Tom.